1. Field of the Invention
The present invention relates to solar collectors, and more specifically to inflatable solar collectors which have fluid flow channels formed therein through which a fluid medium may pass and be heated, i.e., when the collector is inflated and placed in the sun.
2. The Prior Art
Inflatable solar collectors which are constructed using flexible sheet materials and which can be used to heat a fluid medium passing therethrough have been well known for many years. Indeed, many patents are available which describe various types and configurations of such solar collectors; however, none are as easy and inexpensive to manufacture, or as strong in construction as the inflatable solar collectors constructed in accordance with the present invention.
One type of prior art inflatable solar collector is shown in Andrassy, U.S. Pat. No. 3,022,781. The solar collector described in this patent includes two generally rectangularly shaped layers of flexible plastic film which are joined near their peripheries, as well as along parallel portions of their interiors, such that they together form a manifold through which a liquid medium such as water can be passed. Thus water, which is delivered to the manifold via a separate inlet tube, is caused to follow a serpentine flow path as shown in FIG. 1, although other types of flow paths are also contemplated. One of the two manifold-forming plastic film lyers is either pigmented with a radiant energy-absorbent material, or else is coated with such a material, whereas the other layer is transparent, i.e., so as to allow the sun's rays to pass therethrough (this latter layer being the intended "top" layer). The two layers, in addition to being joined near their peripheries and interiorly so as to form the noted fluid flow paths, are suitably joined again along portions of their peripheries so as to create a hem-like space with the other peripheral connection in which respective rods can be inserted so as to provide a rigidity to the four sides of the collector. The collector is inflated by the addition of fluid medium between the two joined flexible plastic film layers. Although it is mentioned that top and bottom insulating spaces can be provided using flexible materials to prevent heat losses, no practical embodiment of such an embodiment is shown or further discussed. Another type of solar collector which is quite similar to that shown in Andrassy is shown in Heitland et al, U.S. Pat. No. 4,143,644.
In Crombie et al, U.S. Pat. No. 4,151,830, an inflatable solar collector is shown which includes a multiplicity of flexible plastic layers which are suitably connected so as to form, in effect, separate lower and upper fluid flow pathways that are each insulated from the surrounding atmosphere. Thus, as shown in FIG. 2, a first fluid flow pathway is created between plastic layers 18 and 19 which are joined internally of their joined peripheries to form a serpentine fluid flow path, and a secondary "return" fluid flow pathway is created between layers 19 and 25, the fluid medium to be heated passing from one path to the other via agitators 20 and valve means 22. Layer 19, and optionally layer 18, are pigmented to absorb solar energy, whereas layer 25 is transparent. The first fluid flow pathway is insulated from the surrounding atmosphere by an insulating air space created between bottom flexible plastic layers 14 and 15, which layers are connected together not only at their peripheries but also at interior portions designated 17; however, they are not connected inwardly of their peripheries to the bottommost layer 18, which layer defines the bottom of the first fluid flow pathway. The secondary fluid flow pathway is insulated from the surrounding atmosphere by an insulating air space created between a top flexible plastic layer 26 and the noted layer 25, layer 26 being transparent to solar radiation and connected not only at its periphery to the periphery of layer 25 but also along lines inwardly thereof as indicated by 27 in FIG. 2. However, no matrix interconnection of multiple flexible plastic layers used for creating multiple insulating air spaces on opposite sides of the fluid flow paths is disclosed.
A further type of inflatable solar collector is shown in Grundmann, U.S. Pat. No. 4,059,095. In this invention two flexible foils are joined at their peripheries as well as along parallel interior portions to form a serpentine fluid flow path for a fluid medium to be passed therethrough and heated, the lower foil being darkened so as to absorb solar radiation and the upper foil being transparent so as to transmit solar radiation. Additional upper and lower foils 32 and 33 can be used to form insulating air chambers around the fluid flow paths formed between foils 30 and 31 (see FIG. 3); however, likewise to the situation in the Crombie patent, no matrix interconnection of multiple flexible plastic layers for creating multiple insulating air spaces on opposite sides of the fluid flow paths is disclosed.
It is an object of the present invention to provide an inflatable solar collector which is not only fabricated using sheets of flexible plastic and which is formed to provide an interior manifold for the flow of fluid medium therethrough, but which is better insulated from the temperatures of the surrounding atmosphere, which is easier and less expensive to manufacture than prior art solar collectors, and which when inflated will provide a product having an extremely strong construction.